1. Technical Field
The present invention relates to a high-strength transmission gear manufactured by a phase controlled nitriding treatment of high-strength nitriding steel, and to a method of manufacturing the same.
2. Description of the Related Art
FIG. 1 is a table showing the composition of carburized steel of a conventional transmission gear, FIG. 2 is a schematic diagram showing a process of manufacturing a transmission gear using the carburized steel of FIG. 1, and FIG. 3 is a graph showing the phase change occurring in the process of manufacturing a transmission gear using the carburized steel of FIG. 1.
Currently, transmission gears are generally manufactured by carburizing. Carburized steel having the composition shown in FIG. 1 is generally used as the carburized steel used to manufacture a transmission gear manufactured by the process shown in FIG. 1. In the manufacturing process shown in FIG. 2, both the surface and core of the transmission gear are highly strengthened. However, since the carburizing is conducted at a temperature of 900° C. or above, the transmission gear is often thermally deformed by a phase change as shown in FIG. 3. Here, since the thermal deformation of the transmission gear cannot be easily predicted, the surface of the transmission gear must be grinded down.
Meanwhile, since a transmission gear produced using the above method has a hardness of 700 Hv or more must be grinded in the grinding process, the cost of transmission gears is quite high (about $2.50 per gear) because takes a lot of time (about 5 minutes for each one) to grind the transmission gear. Therefore, a method of manufacturing a high-strength transmission gear without the need to perform the complicated process described above is needed.
It is to be understood that the foregoing description is provided to merely aid the understanding of the present invention, and does not mean that the present invention falls under the purview of the related art which was already known to those skilled in the art.